How comment out a variable line in a local variable list

Question

In a python file I have

# Local Variables:
# python-shell-interpreter: "python3"
# python-shell-virtualenv-path: "~/.virtualenvs/datascience"
# leo-python-args-to-send: "-f fqanalysis.txt"
# End:

For a couple of days I want to use the python file without the specified virtualenv, so I would like to comment out the line setting python-shell-virtualenv-path, so that next time I open the python file in emacs python-shell-virtualenv-path keeps its global value.

I tried

# ;;python-shell-virtualenv-path: "~/.virtualenvs/datascience"

and

## python-shell-virtualenv-path: "~/.virtualenvs/datascience"

but on opening the python file I always get the error

File mode specification error: (error "Malformed local variable line: ...)

How do I comment out the local variable line correctly?

Answer 1

Based on a quick check of C-hig (emacs) Specifying File Variables, I'm reasonably sure that you can't.

I think your options are:

• Move the comment outside of the local variables block.
• Change the variable (e.g. give it a prefix like DISABLED:) such that the value is simply assigned to a variable which nothing uses.

Edit:

If you don't want to have to approve a bunch of DISABLED:foo variables for safe-local-variable-values, you could adapt the approach to take advantage of the fact that successive entries clobber earlier ones if the same variable name is used. Something like:

# Local Variables:
# #: python-shell-interpreter: "python3"
# #: python-shell-virtualenv-path: "~/.virtualenvs/datascience"
# leo-python-args-to-send: "-f fqanalysis.txt"
# #: <comment>
# End:

These still aren't comments, but it does mean you only have a single local variable named # (or \# in this instance) with the value <comment>, and Emacs won't query you about the earlier ones; so you could re-use this approach in other files and only end up with a single safe-local-variable-values entry for all such 'commented' values, so long as that #: <comment> entry always comes last.

(YMMV; this is only lightly tested, and is obviously a hack workaround. Note also that you needn't use the actual comment character, as it's actually a variable name, so you can call it whatever you want, so long as it's not likely to conflict with any 'proper' variable name.)

You could ditch the need for a #: <comment> entry but still avoid being asked questions if you added the following to your config:

(put '\# 'safe-local-variable (lambda (_) t))

Which says "ALL values for the variable # are safe.